Customer networks are networks established by individuals or companies for internal communication. Customer networks may include local area networks (LAN) or wide area networks (WAN) that comprise a plurality of subscriber devices, such as personal computers, laptops, workstations, personal digital assistants (PDAs), wireless devices, network-ready appliances, file servers, print servers, or other devices. The customer networks may meet customer-specific needs using a number of different communication protocols, such as Asynchronous Transfer Mode (ATM) protocol, Ethernet protocol, Bridged Ethernet protocol, frame relay protocols, or other communication protocols. ATM and frame relay protocols, for example, are frequently used for transport of audio, video, and computer data between source and destination devices within a customer network. Such protocols may transfer information in fixed-length units, such as frames.
According to the Open Systems Interconnection Basic Reference Model (“OSI Reference Model”), both ATM and Ethernet are implemented at the data link layer, also known as layer two (L2) of the network stack. That is, ATM and Ethernet are viewed as L2 protocols. The data link layer provides the means for interacting with the underlying physical layer (L1) to transfer data units between network devices. The Point-to-Point Protocol (PPP) and the Point-to-Point Protocol over Ethernet (PPPoE) are also implemented at the data link layer of the network stack. PPP over ATM and PPPoE are generally implemented over ATM and Ethernet. PPPoE may also be implemented over ATM as PPPoEoA. Accordingly, PPP and PPPoE have been recognized as “upper layer two” protocols, while ATM and Ethernet have been recognized as “lower layer two” protocols.
The third layer (L3) of the OSI Reference Model is referred to as the network layer and is logically viewed as implemented above or on the data link layer of the network stack. The network layer provides the means for transferring data across networks, typically in the form of variable length packets, and may include network routing functions. The Internet Protocol (IP) is the most common example of a network layer protocol. The network layer also provides functionality that may be required by higher layers of the network stack. For example, the network layer maintains quality of service for the transport layer.
Service provider networks include network access devices that provide subscribers with access to the Internet or other networks. For example, multiple subscriber devices may connect to a network switch, e.g., a digital subscriber line access multiplexer (DSLAM), maintained by the service provider network. In many cases, data for the multiple subscriber devices connected to the network access device may be transported over separate physical connections or over a shared physical connection. In any case, the network access device of the service provider typically constructs an interface stack having one or more logical subscriber interfaces to handle communications for each of the subscriber devices. For example, for a given subscriber device, the network access device may configure an interface stack (i.e., a stack of logical interfaces providing functions conforming to the layers of the OSI network model) for a subscriber communicating using PPP over an ATM virtual circuit (VC) or PPPoE over an Ethernet virtual local area network (VLAN) and hence provide connectivity to the Internet. The network access device may create the interfaces of the interface stack statically, dynamically or a combination thereof.